Injury and sepsis are commonly associated with weight loss, hypermetabolism, increased nitrogen excretion and abnormal carbohydrate metabolism. New procedures and techniques are being developed which allow accurate measurements to be made in acutely ill patients without interfering with patient care. These include a special system for prolonged measurement of O2 consumption, CO2 excretion, and 14CO2 excretion -- all performed without the difficulties and artifacts of a mask or mouthpiece. New techniques are being tested for measurement of gas exchange with high inspired oxygen and when mechanical ventilation is required. Indirect calorimetry from gas exchange allows the prolonged study of acutely ill surgical patients by combining daily calorie and nitrogen balance with total body water and cell water to interpret changes in body weight. We are currently analyzing the relative contributions of protein, fat and water to surgical weight loss. Calorie and nitrogen balance provide background data for examining the kinetics of protein breakdown and the relative contributions of C14 alanine and glycerol to the increases in gluconeogenesis as indicated by studies with C14 glucose. Evidence of net gain or loss of body protein will be sought by studies utilizing C14 leucine. Regional uptake or release of glucose and amino acids will be studied by catheterization of the splanchnic viscera and extremity vessels. Animal models will be used to correlate tracer data and regional metabolism. A percutaneous muscle biopsy technique is being used to measure intracellular amino acids, glycolytic intermediates and energy-rich phosphates. The goal is to explain surgical catabolism in terms of altered intermediary metabolism, and to dissect the acute catabolism of trauma from that of major sepsis. These procedures will be used to assay various forms of calorie and nitrogen intake toward more selective guidelines for acute nutritional therapy.